Performance of an oscillatory electrode reactor for electrochemical phosphate removal

Efficient orthophosphate recovery from wastewater is essential for sustainable nutrient recycling. This study evaluated the effectiveness of an oscillatory electrode reactor (OER) employing sacrificial magnesium electrodes for enhanced phosphate removal, improved struvite recovery, and reduced electrode passivation. Baseline experiments in a batch electrochemical reactor (BER) identified optimal operating conditions and subsequently applied them to OER experiments by systematically varying oscillation frequency (0-8 Hz), amplitude (0–10 mm), and initial solution pH (range 4.0-10.0). Results indicated that electrode oscillation significantly improved phosphate removal efficiency, achieving approximately 86% removal compared to 48% without oscillations. Oscillation frequency had a greater influence on phosphate removal than amplitude, with maximum phosphate removal observed at 8 Hz, 10 mm amplitude, and at initial pH ~9.0. Oscillations also significantly reduced electrode passivation, maintaining stable electrode performance. A simplified model correlating phosphate removal enhancement with oscillatory shear rate was developed, achieving excellent agreement (R² = 1) with experimental data. The OER system demonstrates substantial potential as a chemical-free, sustainable, and efficient technology for orthophosphate recovery, supporting wastewater treatment strategies and circular economy objectives. • Electrocoagulation was used to precipitate struvite in an oscillatory reactor. • Oscillation improved maximum orthophosphate removal by 77%. • Oscillation reduced the extent of fouling of the electrodes. • The system removed 97% of total phosphorus and 45% of ammonia from digestate.